@Vero The test I ran was as follows: I had a folder open in Finder (from my local hard drive); there were a mixture of file types eg - .pdf, .msg, .png etc.
With the .msg file selected, I launched Actions (Files, Navigation), the option list appeared and I chose 'open'. The file opened in Outlook. The next day I ran a similar test (though different folder and different .msg file - sorry I can't remember which one) - and the hot key for 'Actions (Files, Navigation)' didn't launch anything. I tried this a few times with different file types in the same folder.
I tried the running the terminal command you recommended, using my own account and the admin account, but got the following error both times: 'tccutil: No such bundle identifier'. Not sure what it means but thought I'd should let you know ....
I have just tried running the file launcher again this morning, and it works fine! (Great - intermittent problems are the best). I did re-start my Mac Mini yesterday but I'm not sure if this would have an effect .....
Maybe close this request and if I have issues again, I will re-lodge.
Thank you very much for your help.